Cracking in polymeric materials, such as thermosetting polymers, can be highly problematic as it leads to the degradation and failure of devices. These cracks occur not only on the surface of the devices, but can also occur on the inside, which are not usually detected by visual inspection. Cracking can cause fiber-matrix interfacial debonding, ply delamination, and simple matrix delamination, which then can lead to degradation and more often than not, complete failure. These cracks can form from thermal and mechanical stresses during the use of the polymeric material. In circuit boards, for example, these cracks can lead to electrical component failure.
In conventional self-healing applications that utilize microcapsules, a catalyst is either blended into the resin along with the microcapsules, or is encapsulated as well, and then blended with the resin-containing microcapsules into a polymeric resin. In these two examples, the crack must be sufficient to expose both the catalyst and the resin (e.g., cracking both a resin-containing capsule and a catalyst-containing capsule). Additionally, in conventional applications, when the catalyst is directly against the microcapsule, the chances of the self-healing agent being released becomes reduced because the catalyst reacts too close to the self-healing agent and essentially closes the capsule, thereby limiting flow into the cracks that have propagated through the polymer.